In recent years, a small cell has been used in order to accommodate the increased data traffic. In this case, “small cell” refers to a cell that has a shorter cell radius or whose number of users that is able to access the cell is smaller compared with a macrocell. A small cell may be established in a macrocell in order to accommodate an increased number of users of the macrocell or increased communications traffic per user. In this case, in order to mitigate interference between the macrocell and the small cell, the small cell is often established so as to perform communication using a frequency bandwidth that is different from a bandwidth used in the macrocell including the small cell.
In order to hand over to a base station of a small cell, a mobile terminal identifies a physical cell ID (PCI, physical cell identifier) allocated to a small cell that is a handover destination. At this point, the mobile terminal performs processing in a frequency bandwidth which the small cell that is a handover destination uses for communication. Thus, a mobile terminal that tries to obtain, during communication with a macrocell, information on a small cell that is a handover destination will perform the processing both in a frequency bandwidth used for communication through the macrocell and in a frequency bandwidth used for communication in the small cell. However, when a mobile terminal performs communication processing in a plurality of frequency bandwidths, power consumption of the mobile terminal increases. Further, a mobile terminal that is located away from a small cell repeats the processing until a physical cell ID is obtained, so power consumption for searching for the small cell further increases.
Therefore, a method in which a mobile terminal determines whether a small cell is in its proximity using fingerprint information has been proposed. The fingerprint information is information generated when a mobile terminal exists in a small cell and stored in a recording medium of a mobile terminal, and includes position information on the small cell such as the position information on the mobile terminal when it existed in the small cell. The mobile terminal identifies a physical cell ID with respect to a small cell determined to be in its proximity, by comparing the position information in a fingerprint stored in the recording medium with a current position of the mobile terminal.
As a related technology, a mobile terminal that stores therein a list indicating an accessible small cell has been devised. When receiving a network policy from a base station, this mobile terminal determines whether a small cell is positionally accessible, using information on an accessible small cell included in the list. Here, fingerprint information is used as information on an accessible small cell. The mobile terminal reports a determination result to the base station. Further, a method in which a base station determines a handover destination for a mobile terminal has also been proposed. In this method, abase station that determines a handover destination reduces, by use of a fingerprint table, the size of a list of a base station that transfers the same physical cell identifier, and identifies a handover destination.                Patent Document 1: Japanese Laid-open Patent Publication No. 2013-31224        Patent Document 2: Japanese Laid-open Patent Publication No. 2011-109666        
In a communication method that uses fingerprint information, when determining that there is a small cell in its proximity using fingerprint information, a mobile terminal starts searching for the small cell. However, the conventional fingerprint information does not include the information on a cell in which the mobile terminal has not existed before. Thus, when using the conventional fingerprint method, a mobile terminal has difficulty in efficiently finding a small cell in which the mobile terminal has not existed before. On the other hand, when searching for a small cell that is a handover destination without using the fingerprint method, a mobile terminal performs search processing even when it is located away from the small cell, so the search processing is not efficiently performed, and further, power consumption of the mobile terminal increases. A method that permits a mobile terminal to efficiently search for a cell established in a bandwidth that is different from a bandwidth used for communication has not been obtained as well.